tailieunhanh - Optical Networks: A Practical Perspective - Part 47

Optical Networks: A Practical Perspective - Part 47. This book describes a revolution within a revolution, the opening up of the capacity of the now-familiar optical fiber to carry more messages, handle a wider variety of transmission types, and provide improved reliabilities and ease of use. In many places where fiber has been installed simply as a better form of copper, even the gigabit capacities that result have not proved adequate to keep up with the demand. The inborn human voracity for more and more bandwidth, plus the growing realization that there are other flexibilities to be had by imaginative use of the fiber, have led people. | 430 WDM Network Elements to using OLTs interconnected back to back or relying on other equipment to handle the passthrough traffic. OADMs are typically deployed in linear or ring topologies. Several types of OADMs are possible with a range of capabilities based on the number of wavelengths they can add and drop the ease of dropping and adding additional wavelengths static or reconfigurable and so on. We studied the basic architectural flavors of OADMs parallel serial and band drop. Each of these has its pros and cons. We also looked at reconfigurable OADM architectures which use tunable filters and or multiplexers as well as tunable lasers in order to provide the maximum possible flexibility in the network. An optical crossconnect OXC is the other key network element in the optical layer. OXCs are large switches used to provision services dynamically as well as provide network restoration. OXCs are typically deployed in a mesh network configuration. As with OADMs several variants of OXCs exist ranging from OXCs with electrical switch cores capable of grooming traffic at STS-1 rates to all-optical OXCs that can switch wavelengths bands of wavelengths and entire fibers. Optical core crossconnects can also be surrounded by optical-to-electrical-to-optical converters to provide some of the grooming and wavelength conversion capabilities offered by electrical core crossconnects but are not suited for grooming traffic at fine granularities such as STS-1 rates. Each has its role in the network. Further Reading Information regarding the various types of OLTs OADMs and OXCs is not easy to come by because many of the commercial implementations are proprietary in nature. Browsing through network equipment vendors Web pages will provide some illustration of the capabilities of the different products in this space. However there are several early testbeds that explored various forms of these network elements. For instance Ale93 Kam96 used a static all-optical OXC that provided

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